<div id="C00000156">
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  <span class="file-title-prefix">Module</span><br />Callbacks<br/>
  In:
<a href="#" onclick="jsHref('files/lib/sass/callbacks_rb.html');">lib/sass/callbacks.rb</a>

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  <div class="description"><p>
A lightweight infrastructure for defining and running callbacks. <a
href="index.html?a=C00000156&name=Callbacks">Callbacks</a> are defined
using \{define_callback\} at the class level, and called using
`run_#{name}` at the instance level.
</p>
<p>
Clients can add callbacks by calling the generated `on_#{name}` method, and
passing in a block that&#8217;s run when the callback is activated.
</p>
<p>
@example Define a callback class Munger
</p>
<pre>
  extend Sass::Callbacks
  define_callback :string_munged

  def munge(str)
    res = str.gsub(/[a-z]/, '\1\1')
    run_string_munged str, res
    res
  end
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<p>
end
</p>
<p>
@example Use a callback m = Munger.new m.on_string_munged {|str, res| puts
&quot;#{str} was munged into #{res}!&quot;} m.munge &quot;bar&quot; #=&gt;
bar was munged into bbaarr!
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  <div class="sectiontitle">Methods</div>
  <ul>
  <li><a href="index.html?a=M001516&name=define_callback" >define_callback</a></li>
  </ul>






<div class="sectiontitle">Protected Instance methods</div>
<div id="M001516" class="method">
  <div id="M001516_title" class="title">
    <b>define_callback</b>(name)
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  <p>
Define a callback with the given name. This will define an `on_#{name}`
method that registers a block, and a `run_#{name}` method that runs that
block (optionall with some arguments).
</p>
<p>
@param name [Symbol] The name of the callback @return [void]
</p>
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<div class="sourcecode">
  <p class="source-link">[ <a href="javascript:toggleSource('M001516_source')" id="l_M001516_source">show source</a> ]</p>
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<pre>
    <span class="ruby-comment cmt"># File lib/sass/callbacks.rb, line 36</span>
36:     <span class="ruby-keyword kw">def</span> <span class="ruby-identifier">define_callback</span>(<span class="ruby-identifier">name</span>)
37:       <span class="ruby-identifier">class_eval</span> <span class="ruby-value str">&quot;def on_\#{name}(&amp;block)\n  @_sass_callbacks ||= {}\n  (@_sass_callbacks[\#{name.inspect}] ||= []) &lt;&lt; block\nend\n\ndef run_\#{name}(*args)\n  return unless @_sass_callbacks\n  return unless @_sass_callbacks[\#{name.inspect}]\n  @_sass_callbacks[\#{name.inspect}].each {|c| c[*args]}\nend\nprivate :run_\#{name}\n&quot;</span>
38:     <span class="ruby-keyword kw">end</span>
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